Nowadays, it is commonly seen that backlight modules are used for electronic devices with flat panel displays, which includes devices as small as hand-held palm pilots and as large as big-screen TVs. Although most backlight modules still adopt cold cathode fluorescent lamp (CCFL), the utilization of light emitting diode (LED) as the light source of large-sized liquid crystal display (LCD) is becoming popular following the advance of LED technology. As the design challenge of a backlight module is to generate uniform illumination across the LCD surface and luminance that is high enough to produce good contrast in a day environment, LED is preferred over CCFL because it has following advantages: (1) as LED is smaller in size than that of CCFL and it is more solid than CCFL as well, not only the assembly of backlight module can be facilitated, but also the backlight modules adopting LEDs as the light source thereof are lighter and smaller comparing to those CCDL backlight modules; (2) it is noted that the color quality of LCDs adopting LED backlight module is better than that of LCDs adopting CCFL backlight module, since LED can provide a wider color gamut as it is being used in the backlight module for LCDs; (3) Comparing to the mercury-contained CCFL, LED is environmental benign.
Although LEDs are preferred, it is required to package an LED light source for enabling the light source package to generate uniform illumination across a specific surface and transferring the LED from point light source into surface light source. Please refer to FIG. 1, which is a cross-sectional view of a LED package disclosed in U.S. Pat. No. 6,679,621, entitled “Side Emitting LED and Lens”. The LED package of FIG. 1 can control the direction of light beams being discharged out of the LED by disposing various refraction surfaces of different shapes at various positions on the LED package, so that the light beams can be emitted out of the LED package in a direction substantially perpendicular to the central axis of the LED package, and thus a side-emitting device with large illuminate areas can be provided. As seen in FIG. 1, light emitted from near focal point F that is directly incident on reflecting surface I is reflected from surface I to refracting surface H and refracted by surface H to exit the lens of the LED package in a direction substantially perpendicular to the central axis of the LED package. Light emitted from near focal point F that is directly incident on refracting surface 156 is refracted by surface 156 to also exit the lens in a direction substantially perpendicular to the central axis. However, it is noted that the LED package of FIG. 1 can only refract light beams emitted by the LED only once by the lens thereof, and moreover, the process for manufacturing the LED package is complicated since it not only requires a step to form a lens on top of an LED while covering the same, it also requires a step of filling the gap between the lens and the LED by a transparent material using a specific pumping-suction means.
Moreover, a LED capsule, disclosed in U.S. Pat. No. 6,682,211, entitled “Replaceable LED Lamp Capsule”, uses a housing having a plurality of microstructures formed thereon for reflecting light beams emitted from a LED. However, the forgoing LED capsule is bulky that it is not suitable to be applied as the light source of LCDs.
In addition, a LED package, disclosed in U.S. Pat. No. 6,670,207, entitled “Radiation Emitter Device Having an Integral Micro-groove Lens”, is able to disperse light emitted from a LED by arranging a lens with micro-grooves in front of the LED. However, as LEDs are not ideal point light sources by themselves, the dispersing of light enabled by the use of the lens with micro-grooves is not as expected, so that the LED package with lens of micro-grooves is not popular.
Therefore, there is a need for an improved LED package structure capable of overcoming the aforesaid shortcomings.